In recent years the petroleum industry has witnessed the development of highly effective novel processes for the synthetic production of gasoline by the conversion of methanol over zeolite type catalyst, particularly medium pore size shape selective aluminosilicate catalyst. Further technological development has broadened the range of this technology to encompass the production of olefins, distillates and aromatics, based on C.sub.1 chemistry and, in particular, methanol.
The ready availability of synthetic methanol from feedstocks such as natural gas, coal and wood provide a broad basis for the production of synthetic gasoline, distillates, olefins and aromatics. Various processes in the aforenoted field of technology are described in the following U.S. patents which are incorporated herein in their entirety by reference: U.S. Pat. Nos. 3,894,107 (Butter, et al); 3,928,483; 4,025,575; 4,252,479 (Chang, et al); 4,025,572 (Lago); 4,328,384 (Daviduk, et al); 4,547,616 (Avidan, et al); 4,450,311 (Right, et al); 3,960,978 and 4,021,502 (Plank, Rosinski and Givens); 4,150,062, 4,211,640 and 4,227,992 (Garwood, et al).
Conversion of olefins to gasoline and/or distillate product is disclosed in U.S. Pat. Nos. 3,960,978 and 4,021,502 (Givens, Plank and Rosinski) wherein gaseous olefins in the range of ethylene to pentene, either alone or in admixture with paraffins, are converted into an olefinic gasoline blending stock by contacting the olefins with a catalyst bed made up of ZSM-5 or related zeolite. In U.S. Pat. Nos. 4,150,062 and 4,227,992 Garwood et al discloses the opcrating conditions for the Mobil Olefin to Gasoline/Distillate (MOGD) process for selective conversion of C.sub.3 + olefins. A fluidized bed process for converting ethene-containing light olefinic streams, sometimes referred to as the Mobil Olefin to Gasoline (MOG) process is described by Avidan et al in U.S. patent application No. 006,407, filed 23 Jan. 1987. The phenomena of shape-selective polymerization are discussed by Garwood in ACS Symposium Series No. 218, Intrazeolite Chemistry, "Conversion of C.sub.2 -C.sub.10 to Higher Olefins over Synthetic Zeolite ZSM-5", 1983 American Chemical Society.
In the process for catalytic conversion of olefins to heavier hydrocarbons by catalytic oligomerization using an acid crystalline metallosilicate zeolite, such as ZSM-5 or related shape selective catalyst, process conditions can be varied to favor the formation of either gasoline or distillate range products. In the gasoline operating mode, or MOG reactor system, ethylene and the other lower olefins are catalytically oligomerized at elevated temperature and relatively low weight hourly space velocity (WHSV). Under these conditions ethylene conversion rate is greatly increased and lower olefin oligomerization is nearly complete to produce an olefinic gasoline comprising hexene, heptene, octene and other C.sub.6 + hydrocarbons in good yield. At elevated pressure olefins are converted to heavier distillate range hydrocarbons as well as gasoline range hydrocarbons, the MOGD process. The production of distillate range products in the MOGD process requires significant process recycle and typically, multiple fixed bed reactors. Accordingly, practitioners in the field are challenged by the need to simplify the overall process to reduce cost while maintaining or improving upon product yields.
It is an object of the present invention to improve the overall operation and cost of the conversion of olefins to gasoline and distillate by process integration with methanol conversion processes.
It is a another object of the instant invention to effect further overall process improvements by the staged conversion of olefins to gasoline at moderate reaction conditions prior to conversion to higher distillate boiling range hydrocarbons.